Generally, heat insulation may be provided for partitions (walls and roofs) of structures by using an insulating material. However, partitions with openings such as doors and windows must be opened and closed with facility and have transparency. It is therefore difficult to apply an insulating material to such partitions over entire areas thereof. The openings having no insulating material applied thereto tend to be defective in terms of heat insulation. Double glazing has been conceived for use in these openings, which includes two sheets of glass joined together with a layer of air formed therebetween to act as an insulating layer.
Such double glazing has a disadvantage that the glass sheets per se are thick and, in combination with the sash, tend to present an unsightly appearance. Thus, a thin and highly insulating double glazing has been conceived, in which two sheets of glass have numerous spacers (corresponding to the above-mentioned first void sustaining elements and in the form of small columns not to be obstructive to transparency) distributed therebetween, and the second void sustaining element disposed between entire edges of the two lass sheets, to provide a decompressed void between the glass sheets.
With the spacers and the second void sustaining element provided, a predetermined void is secured between the glass sheets even if the void is decompressed. This type of double glazing will be described with reference to FIG. 4. Spacers 10 are arranged at basic spacer intervals (hereinafter called basic intervals) 11 which are set based on the strength of glass sheets 1. The intervals between outermost spacers 10a and second void sustaining element 12 (hereinafter called outer intervals) are often determined by calculating down to a fraction, to be within a range not exceeding the basic intervals 11, and by taking the width (or length) of the glass sheets into account. This is because the size of glass sheets usually is not an integral multiple of the above basic interval.
The edges of the two glass sheets are bound by the second void sustaining element. However, where, in the above double grazing, the outer intervals 13 are smaller than the basic intervals 11, atmospheric pressure tends to act less on the outermost spacers 10a than on the other spacers under the influence of the binding force of the second void sustaning element 12. Consequently, the glass sheets impart an insufficient holding force to the spacers, whereby the spacers could easily move between the glass sheets. If the spacers move between the glass sheets, the spacer arrangement becomes unbalanced to impair appearance. In addition, increased variations occur in the stress condition of the glass sheets to reduce their strength.
The object of this invention, therefore, is to provide a double glazing which overcomes the above disadvantage and restrains movement of the first void sustaining elements.